1. Field of the Invention
The present invention relates to a magnetic disk memory comprising a disk pack which has a revolving spindle and a pair of ball bearings disposed on pegs of the spindle, the ball bearings being fixed, braced in the axial direction, to opposite walls of a one-piece supporting shell of a housing, the supporting shell having a cover.
2. Description of the Prior Art
A distinction is generally made in magnetic disk memories between fixed disk memories and interchangeable disk memories. Technical development is continuing to proceed in the direction of higher and higher storage capacities, both in view of the track density and the bit density as the characteristic for the storage capacity per disk surface, on the one hand, as well as in view of the mechanical structure in order to be able to accommodate as many magnetic disks as possible in a prescribed mounting space. An example of this is the so-called 51/4" fixed disk memory whose magnetic disks have an outer diameter of 130 mm and in inner diameter of 40 mm according to the German industrial standard. Analogous to the dimensions of competing floppy disk drives, a mounting space having a mounting height of 82.5 mm and a base area of 146 mm.times.203 mm has crystallized out of this type of storage as a uniform size which is available for the overall apparatus including the housing and the appertaining electronics.
The desire to accommodate as many magnetic disks as possible in this prescribed mounting space is subordinate to the developmental goal of higher storage capacities and to the efforts to increase the recording density on the magnetic disk themselves. Within the scope of this structural attempt, embodiments of 51/4" fixed disk memories have been disclosed in which the drive motor for the disk pack has been miniaturized to such a degree and has been structurally designed such that it can still be built into the hub of the disk pack, even given a prescribed inner diameter of 40 mm for the disk packs. An element which has significant codetermining effect on the overall height of conventional fixed disk memories is therefore integrated in the hub of the magnetic disk pack and the overall height which may be exploited for the disk stack itself is therefore expanded. Based on current conditions in the size of the combined magnetic heads and of the disk thickness, disk packs which contain up to eight magnetic disks stacked on top of one another have therefore become possible. The remaining overall height is required for the housing and for the device electronics.
As mentioned above, the recording density on the magnetic disk is the product of the write density times the track density. A significant criterion for the structural format of a magnetic disk memory also occurs for the case of the present invention, specifically from the track density having, for example, more than 1000 tracks per inch. This high track density requires a best possible vibration-free seating of the spindle of the disk pack in the housing. Requirements are therefore made for this type of storage such as heretofore played a part only given larger disk memories, for example the 14" disk memories.
Given high performance memories conventionally having a larger diameter, it is generally known to seat the spindle of the disk pack at one side in a heavy base plate, in part in structures of a highly-sophisticated design, this particularly applying to interchangeable disk memories wherein the disk pack must be removable from the magnetic storage device. On the other hand, structures are also known in which the spindle is seated at both sides in a rigid housing surrounding the pack. In order to achieve as vibration-free a spindle seating as possible, a fixed bearing and a movable bearing are employed given this two-sided and a spring is provided adjacent the movable bearing, the spring tensing the two bearings relative to one another after assembly such that a coaxial spindle guidance that is as free of axial play as possible is achieved. However, this goal can only be achieved to a limited extent when a combination of fixed and axially movable bearings is employed. Furthermore, additional mounting space is required for the incorporation of the spring, this being lost as useable storage space and taking away valuable space even when the motor is built into the hub.